Hemiballismus

Hemiballismus or hemiballism is a basal ganglia syndrome resulting from damage to the subthalamic nucleus in the basal ganglia. It is a rare hyperkinetic movement disorder, that is characterized by pronounced involuntary limb movements on one side of the body and can cause significant disability. Rarely it affects both sides of the body. Symptoms can decrease during sleep.

Hemiballismus differs from chorea in that the movements occur in the proximal limbs whereas in chorea the limb movements are in the distal limbs. Also in chorea the movements are more dance-like, flowing from one region to another.